POM CNC Machining

Also known as polyoxymethylene. The structure is, abbreviated as POM-C, usually the polymer of formaldehyde polymerization, the polymerization degree is not high, and easy to thermal depolymerization. 1955 years ago DuPont company from formaldehyde polymerization to get formaldehyde homopolymer. Formaldehyde is very easy to crystallize, with a crystallinity of 70% or more. The melting temperature of homopolymerized formaldehyde is about 180℃.

Mechanical properties

Density 1.45g/cm3 Volume resistance VD0303 ≥1015xc

Water absorption 0.8% Surface resistance VDE0303 ≥1013

Chemical resistance - Dielectric constant 1MHz DIN53483 3.8

Continuous use temperature -50~ 90℃ Dielectric loss factor 1MHz DIN53483 0.005

Yield tensile strength 62MPa Dielectric strength VDE0303 85kv/mm

Yield tensile strain 10% Leakage current strength DIN5340 KC600

Ultimate tensile strength - Adhesion

Ultimate tensile strain 40% Non-toxic and non-hazardous EEC90/128 ﹢

Impact toughness 0.B.kJ/m2 Friction coefficient DIN53375 0.35

Notched Impact Toughness 7kJ/m2 Flammability UL94 HB

Rockwell ball hardness 135MPa UV resistance U.V 0

Shore D hardness 85 Acid resistance ﹢

Flexural strength - alkali resistance ‖‖.

Modulus of elasticity 2600MPa Carbonic acid resistance

Vicat softening temperature 150℃ Carbonic acid and water resistance (CKW) 0

Thermal distortion temperature - Resistance to aromatic compounds

Thermal linear expansion coefficient 1.1k-1*104 Ketone resistance

Thermal conductivity 20℃ 0.31w/(mxk) Thermal water resistance

Heat treatment

Drying treatment: If the material is stored in a dry environment, drying treatment is usually not required.

Melting temperature: 190~230℃ for homopolymer material; 190~210℃ for copolymer material.

Mold temperature: 80~105℃. In order to reduce the shrinkage rate after molding, a higher mold temperature can be used.Injection pressure: 700~1200 bar.

Injection speed: Medium speed is common, too slow is easy to produce ripples, and too fast is easy to produce shot lines and shear overheating.

Runners and gates: Any type of gate can be used. If a tunnel-shaped gate is used, a shorter type is preferable. For homopolymer materials, it is recommended to use hot injection.

Nozzle runners. For copolymer materials, both internal and external hot runners can be used.

Back pressure: the lower the better, generally no more than 200 bar

Retention time: If the equipment does not have a melt retention point, POM-H can be retained at 215℃ for 35 minutes; POM-K can be retained at 205℃ for 20 minutes without serious decomposition.

POM-K can stay in the barrel for 7 minutes at 240℃. If the machine is stopped, the barrel temperature can be reduced to 150°C. If the machine is stopped for a long time, the barrel must be cleaned and the heater must be turned off.

Shutdown: Clean the barrel must be made of PE or PP, turn off the electric heat and push the screw in the front position. The barrel and screw must be kept clean. Impurities or dirt can change the superheat stability of POM (especially POM-H). So when finished with halogen-containing polymers or other acidic polymers, apply PE to clean up before playing POM material, otherwise, the explosion will occur. If the role of improper pigments, lubricants, or materials containing GF nylon, it will lead to plastic degradation.

Post-treatment: For the very temperature use of the parts and high-quality requirements, the heat treatment shall be carried out.

Annealing treatment effect, you can put the product into the concentration of 30% hydrochloric acid solution immersed in 30 minutes to check, and then with the naked eye to determine whether there are residual stress cracks generated